Laser Scanning Device, Laser Scanning Method and Program for Laser Scanning

The present invention relates to a surveying technique.

A laser scanning device is known (For example, see Patent document 1).

The Patent Document 1: Japanese U.S. Pat. No. 2,926,521

The present invention relates to a technique to perform setting of scanning conditions appropriate for laser scanning.

The present invention is a laser scanning device including: a distance obtaining unit which obtains distance from the laser scanning device to a specific object, and a condition setting unit which performs setting of conditions to obtain laser scan data which is limited to the specific object, in which the laser scan data which is limited to the specific object is laser scan data of a specific angle range viewed from the laser scanning device, and the specific angle range is set to be relatively narrow in a case in which the distance is relatively long, and is set to be relatively wide in a case in which the distance is relatively short.

In the present invention, an aspect may be mentioned in which conditions are set so that laser scanning density in a unit angle range is set to be relatively large in a case in which the distance is relatively long, and laser scanning density in a unit angle range is set to be relatively small in a case in which the distance is relatively short.

In the present invention, an aspect may be mentioned in which the device further includes: a horizontal rotating unit which rotates horizontally; and a vertical rotating unit which is arranged on the horizontal rotating unit, rotates vertically around horizontal direction regarding rotating axis, and includes an optical unit which irradiates laser scanning light to outside; in which the specific angle range includes angle range of horizontal direction, the angle range of horizontal direction is adjusted based on position in vertical angle direction of the specific object, and in the adjustment, the angle range of horizontal direction is enlarged in a case in which the position in vertical angle direction of the specific object is relatively high vertical angle position compared to a case in which the position in vertical angle direction of the specific object is relatively low vertical angle position.

In the present invention, an aspect may be mentioned in which laser scanning light which is output from the laser scanning device has a cross-sectional shape of longitudinal shape, the laser scanning light performs laser scanning by being reflected by a rotating mirror, the cross-sectional shape of the laser scanning light is rotated depending on direction to which the laser scanning light is reflected by the mirror, and conditions for obtaining the laser scan data are set depending on the direction to which laser scanning light is reflected by the mirror.

The present invention is a laser scanning method using a laser scanning device, including steps of: obtaining distance from the laser scanning device to a specific object, and setting conditions to obtain laser scan data which is limited to the specific object, in which the laser scan data which is limited to the specific object is laser scan data of a specific angle range viewed from the laser scanning device, and the specific angle range is set to be relatively narrow in a case in which the distance is relatively long, and is set to be relatively wide in a case in which the distance is relatively short.

The present invention is a program for control of laser scanning by a laser scanning device made to, when read and executed by a computer processor, cause the computer processor to: obtain distance from the laser scanning device to a specific object, and set conditions to obtain laser scan data which is limited to the specific object, in which the laser scan data which is limited to the specific object is laser scan data of a specific angle range viewed from the laser scanning device, and the specific angle range is set to be relatively narrow in a case in which the distance is relatively long, and is set to be relatively wide in a case in which the distance is relatively short.

According to the present invention, the technique is obtained in which appropriate scanning conditions are set in laser scanning.

1 FIG. 200 300 400 300 400 shows a situation in which a laser scanning deviceand reflecting prismsandbeing target are arranged on a site where point cloud data is needed to be obtained. The reflecting prismsandare arranged at points of which positions in the absolute coordinate system are known. The absolute coordinate system is a coordinate system which is used in maps or GNSS. It should be noted that a local coordinate system can be used as the coordinate system.

1 FIG. In, any objects of scanning other than the reflecting prism are omitted; however, in actual scanning, an object of laser scanning (for example, a ground form or a building) may exist in addition to the reflecting prism.

300 400 300 400 The reflecting prismsandreflect incident light changing the direction by 180 degrees. One which is commercially available for surveying is used as the reflecting prismsand. Other than the reflecting prism, other reflecting member such as a retroreflecting member may be used.

200 200 The laser scanning deviceis arranged at a position appropriate for laser scanning, the position and orientation thereof in the absolute coordinate system are unknown. In this example, the laser scanning deviceperforms first laser scanning of a wide range (for example, all-circumferential scanning) and second laser scanning focusing on the reflecting prism.

200 Here, point cloud data of wide range is obtained by the first laser scanning, the position of each point in the absolute coordinate system is unknown at this step. This is because the position and orientation of the laser scanning devicein the absolute coordinate system are unknown.

300 400 200 Then, positioning of the reflecting prismsandwhich are arranged at known points in the absolute coordinate system is performed by the second laser scanning, and the position and orientation of the laser scanning devicein the absolute coordinate system are calculated by the backward intersection method

200 If the position and orientation of the laser scanning devicein the absolute coordinate system become obvious, a coordinate in the absolute coordinate system is imparted to the point cloud data which is obtained in the first laser scanning, and therefore, point cloud data in the absolute coordinate system is obtained. It should be noted that the number of the reflecting prism can be three or more.

300 400 202 200 300 400 300 400 In the first laser scanning, since reflected light from the reflecting prismsandis too intense, a light receiving unitof the laser scanning devicemay be saturated, and ranging accuracy of the reflecting prismsandmay be deteriorated. That is, in the first laser scanning, positioning accuracy of the reflecting prismsandmay be deteriorated.

300 400 Then, the second laser scanning is performed in order to perform positioning the reflecting prismsandaccurately. During this, input level of a ranging light into a light receiving element is weakened by using a variable optical attenuator in order to obtain high positioning accuracy. This controlling of the variable optical attenuator is performed based on light receiving intensity and distance information of the reflecting prisms which are obtained in the first laser scanning.

202 It should be noted that the saturation due to intense input in the light receiving unitmainly occurs in the light receiving element. If degree of the saturation is small, although output may be distorted or peaked out in the light receiving element, accuracy of ranging may be maintained. However, if degree of the saturation is large, distortion in wave shape of output of the light receiving element may be significant, there may be an error in measurement of distance using phase difference of wave shape and accuracy of ranging may be deteriorated.

The second scanning is performed under condition in which accuracy of later ranging is not adversely affected (condition in which accuracy of ranging is maintained). Practically, the optical attenuator is inserted on an optical path as mentioned above, so as not to saturate the light receiving element. It should be noted that the optical attenuator is arranged in one or both of light emitting optical system and light receiving optical system. Usually, the optical attenuator is arranged in one of the optical systems. In addition, a method is also possible in which light emitting intensity of the light emitting element is weakened.

200 300 200 400 300 400 300 400 200 A distance from the laser scanning deviceto the reflecting prismand a distance from the laser scanning deviceto the reflecting prismare obtained from the results of the first laser scanning. Although these distances may include error, based on the distances, conditions to obtain laser scanning data which is limited to the reflecting prismsandare set. During this, the laser scanning data which is limited to the reflecting prismsandis laser scanning data of a specific angle range which is viewed from the laser scanning device. This specific angle range is set to be relatively narrow in a case in which the distance is relatively long, and is set to be relatively wide in a case in which the distance is relatively short.

2 FIG. 200 200 221 222 221 223 222 224 223 200 shows an exterior appearance of the laser scanning device (laser scanner). The laser scanning deviceincludes a tripod, a base unitwhich is fixed on an upper part of the tripod, a horizontal rotating unitwhich is a rotating body possibly rotating horizontally on the base unit, and a vertical rotating unitwhich is a rotating body possibly rotating vertically with respect to the horizontal rotating unit. The laser scanning deviceis operated by a wirelessly connected external controller (operation terminal) which is not shown.

224 225 225 224 225 The vertical rotating unitincludes an optical unitwhich emits and receives laser scanning light. The optical unitemits laser scanning light (ranging light) as pulsing light. While the vertical rotating unitrotates, this pulsing light emission is performed along a direction perpendicular (vertical surface) to the rotating axis (axis elongating to horizontal direction). In this case, laser scanning light is emitted as pulsing light along direction of vertical angle (elevation angle and depression angle direction) from the optical unit. It should be noted that the vertical angle is measured as 0° regarding horizontal direction and measured as 90° regarding vertical direction.

Two kinds can be mentioned as a structure of optical system.

3 FIG. 201 252 251 252 253 253 224 201 (A) is a conceptual diagram of first structure. In this example, laser scanning light which is emitted from the light emitting unitis irradiated to an oblique mirrorvia an optical combining/splitting unit. The oblique mirroris arranged on top of the vertical rotating memberhaving circular cylindrical shape, at an angle of oblique 45°. The vertical rotating memberrotates vertically in a fashion integrated with the vertical rotating unit, around an axis matching to an optical axis of the light emitting unit(axis elongating to horizontal direction) regarding as a rotating axis.

224 201 252 251 211 202 201 202 223 While rotating the vertical rotating member, laser scanning light is emitted as pulsing light from the light emitting unitso that vertical scanning along vertical surface is performed. Scanning light which is reflected from an object travels along opposite route, passes the oblique mirror surface, the optical combining/splitting unitand the variable optical attenuatorin this order, and finally is received at the light receiving unit. In this structure, the light emitting unitand the light receiving unitare fixed inside of the horizontal rotating unitand do not rotate vertically.

3 FIG. 3 FIG.(A) 3 FIG.(B) 201 202 254 224 (B) shows second structure of the optical system. In this case, the light emitting unit, the light receiving unitand the optical combining/splitting unitrotate vertically in a fashion integrated with the vertical rotating unit. Either structureorcan be employed.

223 224 225 225 By rotating the horizontal rotating unithorizontally, rotating the vertical rotating unitvertically, emitting laser scanning light as pulsing light from the optical unit, and receiving the reflected light thereof from an object at the optical unitsimultaneously, laser scanning with respect to circumference can be performed.

223 223 By scanning along direction of vertical angle as mentioned above (vertical scanning) and rotating the horizontal rotating unithorizontally at the same time, this scanning line along vertical angle direction (vertical scanning line) moves like shifting along horizontal angle direction (horizontal direction). It should be noted that in a case in which horizontal rotation is simultaneously performed during vertical rotation, scanning along vertical angle direction (vertical scanning line) is not completely along vertical direction, and is a slightly oblique line. Here, if the horizontal rotating unitdoes not rotate, scanning along vertical angle direction (vertical scanning line) is along vertical direction.

223 224 223 224 The horizontal rotating unitand the vertical rotating unitrotate by a motor. A horizontal rotating angle of the horizontal rotating unitand a vertical rotating angle of the vertical rotating unitare accurately measured by an encoder.

200 Each laser scanning light is a line of pulse ranging light, and by one laser scanning light, a scanning point which is a reflecting point of the laser scanning light is ranged. Based on this ranged value and irradiation direction of the laser scanning light, position of the scanning point (reflecting point of laser scanning light) with respect to the laser scanning devicecan be calculated.

200 200 As a construction of point cloud data (laser scan point cloud) which is output from the laser scanning device, a construction may be mentioned in which data of distance and direction regarding each point (each scanning point) is output. A construction is also possible in which inside of the laser scanning device, position of each point in a specific coordinate system is calculated and three-dimensional coordinate position of each point is output as point cloud data. In addition, the point cloud data also includes information of luminance of each scanning point (intensity of reflected light).

4 FIG. 4 FIG. 3 FIG. 200 200 200 shows a block diagram of the laser scanning device. An embodiment is also possible in which a part of functional units shown inare constructed separately, and it is attached to the laser scanning device. For example, a construction is possible in which a part of functional units shown inare constructed by a PC (personal computer) or a server, data is sent from the laser scanning deviceto this PC or server, and data is processed therein.

200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 The laser scanning deviceincludes the light emitting unit, the light receiving unit, a ranging unit, a direction obtaining unit, a light emission controlling unit, a driving controlling unit, a reflecting prism detecting unit, a distance to reflecting prism obtaining unit, a reflecting prism direction obtaining unit, a variable attenuator controlling unit, a variable optical attenuator, a scanning conditions setting unit, a point cloud data producing unit, a reflecting prism center calculating unit, a communicating unit, a storing unit, and an action controlling unit.

201 201 225 2 FIG. The light emitting unitincludes the light emitting element emitting laser scanning light, an optical system related to light emission, and a circumferential circuit. Laser scanning light which emitted from the light emitting unitis output from the optical unitshown invia the optical combining/splitting unit. The optical combining/splitting unit is an optical system which splits and combines optical path of outgoing light and incident light by using a half mirror or a dichroic mirror.

202 225 211 202 3 FIG. The light receiving unitincludes the light receiving element which receives laser scanning light, an optical system related to light receiving, and a circumferential circuit. Reflected light of laser scanning light introduced from the optical unitis introduced to the optical combining/splitting unit, the variable optical attenuator, and furthermore, the light receiving unit(See). The variable optical attenuator is explained below.

203 200 202 200 225 The ranging unitcalculates distance from the laser scanning deviceto the reflecting point (scanning point) of laser scanning light based on output of the light receiving unit. In this example, a reference optical path is arranged inside of the laser scanning device. Laser scanning light which is output from the light emitting element is divided into two ways, and one of them is irradiated from the optical unitto an object as laser scanning light, and the other is introduced into the reference optical path as reference light.

225 202 200 Laser scanning light which is reflected from the object and introduced from the optical unitand the reference light which propagated in the reference optical path are combined and input into the light receiving unit. Since propagated distance is different between laser scanning light and reference light, reference light is detected at the light receiving element first, and then laser scanning light is detected at the light receiving unit. Here, with reference to output wave shape of the light receiving element, detected wave shape of reference light is output first, and after a time lag, detected wave shape of laser scanning light is output. From phase difference (time difference) of two wave shapes, distance from the laser scanning deviceto reflecting point of laser scanning light is calculated. It should be noted that a construction is also possible in which distance is calculated based on flight time of laser scanning light.

204 204 204 204 a b. The direction obtaining unitobtains direction of optical axis of laser scanning light. The direction of optical axis is obtained by measuring angle of optical axis in horizontal direction (horizontal angle) and angle of optical axis in vertical direction (vertical angle: corresponding to elevation angle or depression angle). The direction obtaining unitincludes a horizontal angle detecting unitand a vertical angle detecting unit

204 223 204 224 a b The horizontal angle detecting unitdetects horizontal rotating angle of the horizontal rotating unit. The horizontal rotation is a rotation around a vertical direction regarding as a rotating axis. Detection of angle is performed by an encoder. The vertical angle detecting unitdetects vertical rotating angle (elevation angle or depression angle) of the vertical rotating unit. The vertical rotation is a rotation around a horizontal direction regarding as a rotating axis. Detection of angle is performed by the encoder.

223 224 200 By measuring the horizontal rotating angle of the horizontal rotating unitand the vertical rotating angle of the vertical rotating unit, direction of optical axis of laser scanning light which is viewed from the laser scanning device, that is, direction of scanning point becomes obvious.

205 201 206 206 223 206 224 a b The light emission controlling unitcontrols light emitting timing of laser scanning light in the light emitting unit. The driving controlling unitincludes a horizontal rotating driving controlling unitfor controlling driving for horizontal rotation of the horizontal rotating unitand a vertical rotating driving controlling unitfor controlling driving for vertical rotation of the vertical rotating unit.

207 202 The reflecting prism detecting unitidentifies and detects reflected light from the reflecting prism based on output of the light receiving element of the light receiving unitin the first laser scanning. Ranging light which is reflected at the reflecting prism has several orders of magnitude more intense than other reflected light. Using this difference in intensity, the reflected light from the reflecting prism is detected among received reflected lights.

Furthermore, since intensity of reflected light from the reflecting prism is intense, output wave shape of the light receiving element which received reflected light from the reflecting prism shows a saturated wave shape. Practically, top of the wave shape is flattened, and the wave shape is output in a condition having a lasting effect longer than light receiving time. By identifying this peculiar output wave shape, reflected light from the reflecting prism can be detected among many kinds of reflected light.

208 200 207 207 203 202 208 The distance to reflecting prism obtaining unitobtains distance from the laser scannerto the reflecting prism which is detected by the reflecting prism detecting unit. Reflected light from the reflecting prism which is detected by the reflecting prism detecting unitis specified, and the distance is measured by the ranging unit. In the first laser scanning, reflected light from the reflecting prism is especially intense, the light receiving element of the light receiving unitis saturated, and accuracy of ranging is deteriorated. Therefore, distance information to the reflecting prism which is obtained by the distance obtaining unitin the first laser scanning contains error.

211 It should be noted that in the second laser scanning, since intensity of laser scanning light which is input in the light receiving element is adjusted by using the variable optical attenuator, distance can be measured accurately. Also in the second laser scanning, determination whether or not a light is the reflected light from the reflecting prism is performed using difference of light receiving intensity.

209 200 207 204 The reflecting prism direction obtaining unitobtains direction of the reflecting prism from the laser scannerwhich is detected by the reflecting prism detecting unit. This direction is obtained from the direction obtaining unit.

210 211 211 202 210 202 203 The variable optical attenuator controlling unitcontrols attenuating amount in the variable optical attenuatormentioned below. The variable optical attenuatorattenuates incident light in the light receiving unit. This attenuating amount (attenuating ratio) is variable. Controls for varying attenuating amount is performed in the variable optical attenuator controlling unitbased on light receiving intensity in the light receiving unitand distance to an object which is calculated by the ranging unit. This technique is disclosed in Japanese Unexamined Patent Application Publications Nos. 2022-112957 and 2022-112959, for example.

211 As the variable optical attenuator, a type in which transmittance is adjusted by rotating a circular plate having semi-transmissive in which transmittance is set to gradually change along a circumferential direction, a type in which transmittance of liquid crystal is controlled, or the like, may be mentioned. A module of variable optical attenuator is commercially available, and an appropriate one can be selected among them.

Since reflection from the reflecting prism is intense, the light receiving element is saturated and error may occur in ranging value of the reflecting prism in the first laser scanning. For example, according to the inventors'experiment, it is obvious that error of centimeter level may occur in reflected light from the reflecting prism in a laser scanner which can range at an accuracy having error of several millimeter. Although this degree of increase in error results from non-linear action of the light receiving element and is not constant, it may be about several times to ten times of typical measurement error.

207 202 202 201 By arranging the variable optical attenuatorin front of the light receiving unit, intensity of light which is input in the light receiving unitis weakened and the above problem due to saturation in the light receiving element is restrained. It should be noted that a construction is also possible in which the variable optical attenuator is arranged in front of the light emitting unit.

212 212 The scanning condition setting unitsets scanning conditions of the second laser scanning which is focused on the reflecting prism. To avoid redundant laser scanning and obtaining redundant laser scan data, the second laser scanning for accurate positioning of the reflecting prism is performed with respect to a limited range which is focused on direction of the reflecting prism. Setting of the scanning conditions during this is performed in the scanning condition setting unit. The scanning conditions include angle range in which scanning data is obtained and scanning density. In the case of this example, the angle range for obtaining scanning data is determined by a range of horizontal angle and a range of vertical range.

The scanning density is a density of scanning with respect to object of scanning. Practically, it is a density of reflecting point. A high scanning density corresponds to a situation in which reflecting points gathered finely and gaps among adjacent reflecting points are small. On the other hand, a low scanning density corresponds to a situation in which distribution of reflecting points is rough (sparse) and gaps among adjacent reflecting points are large.

Controlling of scanning density is performed by varying scanning rate and/or oscillating frequency of pulsing light emission. Since varying oscillating frequency is not general, scanning density is controlled by controlling scanning rate ordinary.

223 223 Practically, in order to increase scanning density in horizontal direction, rotation rate of the horizontal rotating unitduring scanning is decreased. In a case in which oscillating frequency of the laser scanning light is constant, the number of laser scanning light in a unit angle range in horizontal direction becomes large by slowing rotating rate of the horizontal rotating unit, thereby increasing density of scanning point (reflecting point of laser scanning light) in horizontal direction.

224 By a similar principle, in order to increase scanning density in vertical direction, rotating rate of the vertical rotating unitis decreased during scanning. The opposite tendency is employed in order to decrease scanning density.

The above setting of scanning conditions is determined based on two elements, that is, (Element 1) distance to an object of positioning and (Element 2) vertical angle of the object of positioning. (Element 1)

In setting of scanning conditions regarding the element 1, range of vertical angle and range of horizontal angle for obtaining scanning data is controlled corresponding to distance L. Hereinafter it is explained in detail.

It should be noted that scanning of horizontal direction is performed with respect to a limited angle range which includes the predetermined range, and within the range, scanning data of the range of horizontal angle which is set, is obtained as point cloud data (obtaining as data to use).

Regarding a limited scanning range in vertical angle direction, since an operation stopping scanning only in a specific vertical angle range is mechanically difficult, actually, scanning of all circumferential range (vertical rotation 360°) is performed, and data is obtained as point cloud data only in a specific angle range.

In this way, burden to hardware can be reduced, and data region used can be reduced. Of course, a construction is not excluded in which scanning is performed in the specific angle range.

5 FIG. 5 FIG. 1 1 2 2 1 2 shows a case in which the laser scanning device is arranged at point O and laser scanning data is obtained limitedly in horizontal angle range and vertical angle range of a certain range.shows a scanning rangein a case in which distance from the laser scanning device is Land a scanning rangein a case in which distance from the laser scanning device is L, under conditions of the same horizontal angle range and vertical angle range. As is obvious from comparing the scanning rangeand the scanning range, even if conditions of horizontal angle range and vertical angle range are same, scanning range (area to which scanning is performed) is different since distance is different. Practically, if conditions of horizontal angle range and vertical angle range are same, scanning range may be larger as distance is longer.

Scanning of narrow range (the second scanning) which is for the reflecting prism is set to be performed with respect to a limited scanning range of square of about 10 cm to 1 m around center of position of the reflecting prism which is obtained in the first laser scanning (this includes error due to saturation of the light receiving element).

H V H V H V V H V For example, at a position where there is assumed the reflecting prism is arranged, it is assumed that a range of distance H in horizontal direction and distance V in vertical direction is scanned. In this case, if it is assumed that distance to the reflection prism is L, scanning range in horizontal angle is θ, and scanning range in vertical angle is θ. In a case in which angle range is sufficiently small, if Lθ=H and scanning range in vertical angle is θ, θand θshould be set so as to satisfy Lθ=V. As is obvious from this calculation formula, in a case in which V and H are fixed, θand θcan be small value if L is large. There is the opposite tendency if L is small (a case in which distance is close).

H V Setting of scanning based on the element (1) is performed by the above principle based on distance data L to the reflecting prism which is obtained in the first laser scanning. Practically, the above H and V are imparted, and θand θare set based on L.

H V 223 224 Furthermore, under a condition in which L is large and θand θare small, scanning rate is slowed. Practically, rotating rate during scanning of at least one of the horizontal rotating unitand the vertical rotating unitis slowed. In this way, decrease in scanning density is suppressed in a place at which L is large.

That is, with respect to an object for which L is large (distance is long), compared to a case in which L is small, decrease in scanning points density is suppressed in a place of distance L by increasing relatively the number of laser scanning lights in a unit angle range.

In setting of scanning range regarding the element 2, it is necessary that horizontal angle range of scanning is enlarged proportional to vertical angle. It should be noted that horizontal angle range should be all circumference near the vertex.

200 2 FIG. In the laser scanning devicewhich is exemplified inin which horizontal rotation and vertical rotation are combined, even if angle range for deciding scanning range in horizontal direction is the same, an area to be scanned at a specific distance is varied depending on angle of vertical angle.

9 FIG. 1 1 shows a principle diagram. For example, it is assumed that a specific distance range of horizontal direction (circular arc) is set at a specific distance of vertical angle 0° (elevation angle 0°: horizontal direction). Angle range of horizontal angle corresponding to the circular arcis Δθ. It should be noted that vertical angle is defined as 0° for horizontal direction and 90° for vertically upward (vertex).

9 FIG.(A) 9 FIG.(A) 1 2 1 2 As shown in, in the scanning combining horizontal rotation and vertical rotation, as vertical angle becomes larger, scanning range in horizontal direction corresponding to angle range Δθ of horizontal angle is decreased from range of circular arcto range of circular arc. As is obvious from, distance of the circular arcis longer than distance of the circular arc. As closer to the vertex (vertical angle 90°), distance of circular arc may be shorter. At the vertex (vertical angle 90°), distance of circular arc corresponding to range of horizontal angle may become 0.

1 1 2 9 FIG.(B) That is, in a case in which scanning range Δθ in horizontal angle corresponding to range of the circular arcin horizontal direction is set, as vertical angle becomes higher (higher elevation angle), scanning range considered as distance of horizontal direction becomes narrower. As a result, as shown in, in the setting of angle range of same horizontal angle, scanning range may change (be decreased) from Sto Sdepending on vertical angle.

9 FIG.(B) 1 2 1 2 1 2 1 2 In the case of, during scanning in the setting of same horizontal angle range, if scanning range which is considered as area in horizontal direction (a range almost vertical angle 0°) is S, at high vertical angle, scanning range which is considered as area is decreased to S. Compared to S, the area of Sis decreased at amount of reduced horizontal direction range (difference between the circular arcand the circular arc). That is, the area of scanning range becomes narrow. Therefore, at a place at which vertical angle is large, it is necessary that range of horizontal angle is intendedly enlarged, and difference of the area between Sand Sis needed to be corrected.

9 FIG. 2 2 As an extreme value, in the vertex part (vertical angle=90°), horizontal angle range should be enlarged to all circumference (360°). For example, in a case in which a circular scanning range exists near the vertex as shown in, data near the vertex can be obtained by rotating horizontal angle at 360° in a range from vertical angle(for example, 85° or the like) to the vertex angle (90°). In that case, by eliminating scan data of a range from vertical angle=0° to vertical angle, appropriate scan data can be obtained.

Hereinafter, one example of optimization of scanning conditions considering the above element 1 and element 2 is explained.

200 200 200 Here, a practical example is shown. It should be noted that an object is a reflecting prism. First, from a result of a first laser scanning, point cloud data is extracted based on reflected light from the reflecting prism, and distance L and vertical angle from the laser scanning deviceto the reflecting prism are obtained. Although this distance L includes error due to intense reflected light, it can be used unproblematically in setting of range of a second laser scanning. The vertical angle is an angle of vertical direction of the reflecting prism which is viewed from the laser scanning device. If the reflecting prism is viewed in horizontal direction viewed from the laser scanning device, the vertical angle is 0°.

1 Adjustment regarding the elementis performed as follows. Here, scanning range for searching the reflecting prism is Hm in horizontal direction and Vm in vertical direction. This range is preliminarily set based on size of the reflecting prism. For example, in a case in which an appearance size of reflecting surface of the reflecting prism is a circle having diameter of 5 cm, considering an extra size, a range of H=10 cm and V=10 cm is set as scanning range. During this, scanning range is determined so that the point which is reflecting center of the reflecting prism obtained in the first laser scanning positions at the center of scanning range.

H V H V H V Here, scanning range of horizontal angle is θ(rad) and scanning range of vertical angle is θ(rad). θand θare calculated so as to satisfy Lθ=H and Lθ=V.

11 FIG. 11 FIG. H V As a simple way, a method may be mentioned in which a correction curve shown inis preliminarily prepared, and angle range of left vertical axis is selected as θ(deg) and θ(deg) depending on distance L.shows a correction curve in a case in which range of square about 10 cm in vertical and horizontal is selected as scanning range.

11 FIG. 11 FIG. 223 124 Right vertical axis inis a scanning rate. In setting of scanning rate shown in, as distance L is longer, scanning rate is slowed so as not to reduce scanning density. Scanning rate is controlled by controlling rotating rate of the horizontal rotating unitand the vertical rotating unit.

223 214 Practically, if rotating rate of horizontal rotation of the horizontal rotating unitis slowed during scanning, scanning density in horizontal direction (density of scanning points) is increased. Furthermore, if rotating rate of vertical rotation of the vertical rotating unitis slowed during scanning, scanning density in vertical direction (density of scanning points) is increased.

223 224 Ideally, it is desirable that scanning rate is controlled so as to suppress decrease in scanning density in both of the horizontal rotating unitand the vertical rotating unit.

2 1 9 FIG. H Then, with respect to the result considering the element 1, correction is performed considering the element 2. Regarding the element, a correction coefficient k (1≤k) for the circular arc(vertical angle=0°) incorresponding to vertical angle is calculated preliminarily, and the above θis corrected using this correction coefficient k. The correction coefficient k is increased in proportion to vertical angle.

H 10 FIG. If vertical angle is increased, corrected value of scanning range in horizontal direction is kθ. For example, an example may be mentioned in which k is calculated by k=1/cosθ (θ: vertical angle, but excluding θ=90°). It should be noted that in a case in which vertical angle is 90°, scanning range in horizontal direction is all circumference (360° around horizontal direction, see).

213 The point cloud data producing unitproduces point cloud data based on results of laser scanning. The point cloud data is a data of distance and direction regarding each point (each scanning point) and a data of luminance (intensity of reflected light) of each scanning point.

223 212 In this example, limited scanning in horizontal direction is performed by horizontally rotating the horizontal rotating unitin the limited angle range. Actually, considering extra range to some extent, horizontal rotation is performed in a slightly wider range, and among scan data obtained during this, scan data of preliminary determined horizontal angle range is extracted as point cloud data. This predetermined horizontal angle range is set in the scanning condition setting unit.

224 212 At the same time, scanning in vertical direction is performed while rotating the vertical rotating unitvertically in all circumference. Then, among all circumference scan data which is obtained, scan data of preliminary determined vertical angle range is extracted as point cloud data. This predetermined vertical angle range is set in the scanning condition setting unit.

213 In this way, scan data of horizontal angle range and vertical angle range which is preliminarily determined is extracted as point cloud data. This processing is performed in the point cloud data producing unit. Since unnecessary scanning point is not handled as a data, burden for operation is reduced, and data capacity is suppressed from consumed.

214 The reflecting prism center calculating unitcalculates position of reflecting center of the reflecting prism based on point cloud data of the reflecting prism obtained by laser scanning. Practically, position of gravity center is calculated from multiple point cloud data obtained by reflected light from the reflecting prism, and the position is calculated as reflecting center of the reflecting prism. It should be noted that due to accuracy of basic point cloud data, accuracy of positioning of the reflecting prism based on the result of the first laser scanning is relatively low, and accuracy of positioning of the reflecting prism based on the result of the second laser scanning is relatively high.

215 216 200 217 200 The communicating unitcommunicates with an external controller or other device not shown. Communicating is performed using wired or wireless LAN, portable phone lines, and the like. The storing unitis constructed by a semi-conductor memory or hard disk device, and stores action program necessary for action of the laser scanning device, data, data resulting from process of action or result of action. The action controlling unitis a computer performing action control of the laser scanning device.

3 FIG.(A) Hereinafter rotation of cross-sectional shape of laser scanning light (ranging light) beam which generates in a case in which vertical scanning (perpendicular scanning) ofis employed is explained.

With considering this rotation of cross section of laser scanning light beam, scanning conditions and content of processing of scanning data can be determined.

6 FIG. 6 FIG.(A) 601 601 601 is a principle diagram showing the principle in which cross-sectional shape of ranging light beam rotates accompanied by rotation of the reflecting mirror.shows a case in which laser scanning light having flattened beam cross section which is longitudinal along Y axis direction enters from positive direction of X axis to the mirror. Component of normal vector of reflecting surface of the mirrorin this case is (X, Y, Z)=(1,−1,0). In this case, laser scanning light is reflected to negative Y axis direction by the mirror. Longitudinal direction of cross section of this reflected light is X axis direction.

6 FIG.(B) 6 FIG.(A) 601 shows a situation in which the mirroris rotated at 90° around X axis as a rotating axis (rotating 90° anticlockwise viewed from negative X axis direction) from the situation in.

6 FIG.B 601 601 In the case of, component of normal vector of reflecting surface of the mirroris (X, Y, Z)=(1, 1, 0). In this case, laser scanning light is reflected to positive Z axis direction by the mirror. Longitudinal direction of cross section of this reflected light is Y axis direction as same as incident light.

601 6 FIG.(A) 6 FIG.(B) 7 FIG. 7 FIG. Here, change in longitudinal direction of beam cross section of reflected light during the mirroris rotated little by little from the situation ofto the situation of, is considered.shows this situation. As shown in, in a case in which the mirror is rotated and vertical scanning is performed, beam cross section which had longitudinal direction in X axis direction in horizontal direction is rotated accompanied by increasing vertical angle (elevation angle from horizon is increased), and beam cross section has longitudinal direction in Y axis direction at 90° of vertical angle (vertical direction).

8 FIG. 8 FIG. 8 FIG. shows one example of relationship between vertical angle and rotation of beam cross section.shows a situation in which laser scanning light having elliptic beam cross section is rotated depending on difference of vertical angle.shows a situation in which elliptic beam having longer axis in horizontal direction at low vertical angle is rotated as vertical angle is increased, and beam size in H direction and beam size in V direction change.

It should be noted that in a case in which cross section of beam which enters into the mirror is circular shape, the above influence of rotation does not occur. In addition, in a case in which cross section of beam which enters into the mirror is square shape, the above influence of rotation occurs in a precise sense; however, it is not a problem in particular.

6 8 FIGS.to Hereinafter one example of controlling related to rotation of beam cross section which is exemplified inis explained. Here, setting of scanning range in the second laser scanning is considered.

8 FIG. As shown in, in a case in which cross section of laser scanning light is longitudinal, beam diameter (size of beam cross section) in V direction and H direction changes depending on vertical angle. Here, for example, in a case in which degree of overlapping of scanning light is optimized at vertical angle 0° (horizontally long beam), there is a possibility that gap along horizontal direction is generated at high vertical angle.

In this case, according to vertical angle position of beam center, scanning density of H direction is increased at high vertical angle. In addition, in this case, since the beam may be vertically long at high vertical angle and excessively overlap in V direction, scanning density of V direction is decreased. Actually, since variation adjustment of scanning rate in V direction is not appropriate, density of point cloud data being obtained is adjusted depending on vertical angle (in other word, adjusting density of eliminating). In this way, scanning density of V direction is controlled.

8 FIG. In addition, in a case in which the beam cross section is vertically long at vertical angle 0° opposite to the case of, since the beam cross section may be horizontally long at high vertical angle, and depending on scanning conditions, there is a possibility that gap is generated in scanning of V direction. In this case, scanning density of V direction is increased at high vertical angle.

12 FIG. 12 FIG. 216 217 is a flowchart diagram explaining one example of steps of processing. A program executing the processing ofis stored in the storing unitor an appropriate storing medium, and executed by CPU of computer constructing the action controlling unit.

1 FIG. 101 300 400 200 First, the first laser scanning is performed under the condition of(Step S). Here, the positions in the absolute coordinate system of the reflecting prismsandare known, and the position and orientation in the absolute coordinate system of the laser scanning deviceis unknown. As a coordinate system, a local coordinate system can be used. The first laser scanning is performed for an object such as ground form, building or the like, and is performed with respect to all circumference under a general condition in which dimming taking into account intense reflection from the reflecting prism is not performed.

300 400 102 Among scanning data obtained by the first laser scanning, scanning data regarding reflection from the reflecting prismsandis extracted (Step S). This processing is performed based on light receiving intensity of laser scanning light detected or detected wave shape thereof.

102 103 300 400 200 102 104 1 200 300 2 200 400 300 200 400 200 Next, position of gravity center of scanning data obtained in Step Sis calculated (Step S). In this way, positions of reflection center of the reflecting prismsandare determined. Next, distance (separated distance from the laser scanning device) to the gravity center position which is calculated in Step Sis obtained (Step S). In this way, distance Lfrom the laser scanning deviceto the reflecting prismand distance Lfrom the laser scanning deviceto the reflecting prismare obtained. In addition, direction of reflection center of the reflecting prismviewed from the laser scanning deviceand direction of reflection center of the reflecting prismsviewed from the laser scanning deviceare obtained.

5 FIG. 105 300 1 400 2 Next, by the method explained above related to, scanning range is set according to distance considering the element 1 (Step S). Here, setting of scanning range for accurate scanning of the reflection prismaccording to the distance Land setting of scanning range for accurate scanning of the reflection prismaccording to the distance Lare performed.

105 300 300 105 400 400 105 In Step S, the scanning range according to distance to the reflecting prismis set in a situation in which direction of the reflecting prismis center. Furthermore, in Step S, the scanning range according to distance to the reflecting prismis set in a situation in which direction of the reflecting prismis center. It should be noted that the scanning range is set in a situation vertical angle is 0° in Step S.

105 2 106 9 FIG. Next, with respect to the scanning range obtained in Step S, the scanning range is set (corrected) considering the element(Step S). As explained related to, since the scanning range becomes narrower as vertical angle is higher, in this processing, the scanning range is enlarged intendedly at high vertical angle. It should be noted that as a singular value, in a case in which vertical angle is 90°, a range of horizontal angle 360° is the scanning range (however, obtaining range of vertical scanning data is limited

106 107 106 After Step S, the second laser scanning is performed (Step S). The second laser scanning is performed to the scanning range in which a specific range obtained at a step after Step Sis focused on.

211 202 202 In the second laser scanning, the variable attenuatoris inserted in front of the light receiving unit, so that intensity of laser scanning light input into the light receiving unitis decreased. In this way, saturation in the light receiving unit is avoided, and deterioration in ranging accuracy is restrained. Degree of dimming is adjusted based on intensity of detected light obtained in the first laser scanning and distance to the reflecting prism being an object.

106 For example, if the scanning range obtained in Step Sis 90° to 91° of horizontal angle range and 5° to 6° of vertical angle range. It should be noted that horizontal angle is measured as 0° for north direction viewed from vertically upward, and is measured clockwise. Vertical angle is measured as 0° for horizontal direction and 90° for vertically upward.

In this case, scanning range in horizontal angle is set 3° to 8° for an extra range, and among scanning data obtained in the range, scanning data of range of 5° to 6° is employed. Scanning in vertical direction is performed with respect to all circumference (360°), and among scanning data obtained, scanning data of range of 0° to 1° is employed. In this way, processing can be performed efficiently.

300 400 108 300 400 109 Next, positions of gravity center of scanning data of the reflecting prismsandobtained by the second laser scanning are calculated (Step S), and positions of reflection center of the reflecting prismsandare obtained based on the positions of gravity center (Step S). Since position data obtained here has no problem of saturation in the light receiving element, accuracy is high.

300 400 200 110 200 111 After the positions of the reflecting prismsandare obtained, position and orientation in the absolute coordinate system of the laser scanning deviceis calculated by the backward intersection method (Step S). After the position and orientation in the absolute coordinate system of the laser scanning deviceare calculated, by using them, position in the absolute coordinate system of each point of point cloud data obtained by the first laser scanning is calculated (Step S).

110 111 200 109 110 111 Processing of Steps Sand Sare performed by using a computer for data processing, not using the laser scanning device. That is, the data of Step Sis sent to the computer for data processing, and processing of Steps Sand Sare performed therein.

According to the present embodiment, appropriate scanning conditions are set in laser scanning. In this way, processing can be efficient.

200 221 223 224 225 : Laser scanning device,: tripod,: horizontal rotating unit,: vertical rotating unit,: optical unit.